Main Processes for Producing PO in China
2020-09-16    [Source:PUdaily]
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PUdaily, Shanghai—— Today, PUdaily will introduce you to major processes for producing propylene oxide (PO) in China, including chlorohydrination process, cooxidation process, CHP process and direct oxidation proccess. Cooxidation process includes PO/SM and PO/TBA-MTBE, and direct oxidation process mainly refers to HPPO.

Chlorohydrination process:

Chlorohydrination process is a process using propylene, chlorine and calcium hydroxide (or sodium hydroxide) as raw materials to produce PO through chlorohydrination and saponification. As the process is simple it currently plays a dominant role in China (as shown in Figure 1).

Fig. 1 Producing PO using chlorohydrination process

Source: PUdaily

As a mature process, chlorohydrination process is energy efficient and requires low investment. But it produces a large amount of industrial wastewater, waste gases and residues and is corrosive to equipment. Domestic manufacturers using this process are concentrated in Shandong, including Xin Yue Chemical, Befar Group and Jinling Chemical.

Cooxidation process:

Cooxidation process, also known as indirect oxidation process, includes PO/SM process and PO/TBA (or MTBE) process, which respectively use ethylbenzene and isobutane to produce tert-butyl alcohol and styrene through co-oxidation, and meanwhile co-produce propylene oxide. The process flows are shown in Figures 2 and 3.

 

Fig. 2 Producing PO using PO/SM process

Source: PUdaily

Fig. 3 Producing PO using PO/TBA (or MTBE) process

Source: PUdaily

Unlike chlorohydrination process, this process does not produce waste water and waste residue. Besides, revenue generated by co-products could to some extent reduce the total cost. The disadvantage is that the process is complex and requires heavy investment. Presently, domestic manufacturers using PO/SM process include CNOOC and Shell Petrochemicals and Ningbo ZRCC Lyondell Chemical, and those using PO/TBA (or MTBE) process include Wanhua and Nanjing Jinling Huntsman New Material.

CHP process:

CHP process does not produce co-products. The process produces PO by using cumene hydroperoxide to oxidize propylene. Using peroxide the by-product dimethyl benzyl alcohol is converted into cumic alcohol, which is converted back to cumene through hydrogenation. The process flow is shown in Figure 4.

Fig. 4 Producing PO using CHP process

Source: PUdaily

Traditionally, oxidizing cumene takes a lot of time and is inefficient. And as the oxidizing equipment is large, huge investment is required. At present, the domestic manufacturers using this process include Taixing Chemical.

HPPO proccess:

HPPO proccess makes PO using hydrogen peroxide to oxidize propylene. The process flow is shown in Figure 5.

Fig. 5 Producing PO using HPPO process

Source: PUdaily

The process is simple and highly value-added, does not produce poisonous or hazardous gases and produces few by-products. The process is environment-friendly as water produced in the reaction can be recycled. Domestic manufacturers using this process include Jishen Chemical Industry and Sinopec Changling Petrochemical.

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